The invention relates to a gas valve unit for controlling gas throughput guided to a gas burner of a gas device, in particular a gas cooking appliance, wherein the gas valve unit has an actuation mechanism for a magnetic valve.
In this invention the gas valve unit has a valve housing and an actuation shaft for adjusting an opening cross section of the gas valve unit and an additional stop valve, wherein a movement of the actuation shaft is able to be transmitted to the stop valve by means of a linearly-displaceable connection element.
Gas valve units of the said type with a stop valve are frequently also referred to as safety gas valves. As a rule a rotary knob with an actuation shaft is pushed onto a control section of the gas valve unit, which an operator of the gas cooking appliance can access manually. The opening cross section of the gas valve unit is generally adjusted by turning the actuation shaft. The stop valve can be opened by the operator by axial displacement of the actuation shaft, in that they push on the rotary knob. The axial movement of the actuation shaft is transmitted to a linearly-displaceable connection element. This movement of the actuation shaft can be transmitted to the connection element directly or indirectly, for example via a device for redirecting the direction of movement. The connection element is in contact directly or indirectly with a stop element of the stop valve. With an axial movement of the connection element in the direction of the stop element, said stop element can be lifted away from a valve seat and thereby the stop valve can be opened.
Usually the stop valve also has a magnet unit with which the stop element can be held in the open position after the stop element has been put into this open position manually by pushing the actuation shaft. The magnetic force able to be created with the magnet unit is not sufficiently large however to move the stop element, starting from its closed position, into the open position. As a rule the magnet unit contains a wound coil which is connected to a thermoelement disposed in the area of the gas burner. The electrical voltage created with the thermoelement causes a current to flow through the coil of the magnet unit and thus creates a magnetic force which keeps the stop valve open for as long as a gas flame is burning at the gas burner. When the gas flame is extinguished, the stop valve closes automatically and can only be opened again by manually pushing the actuation shaft.
With these conventional gas valve units there is the problem that the stop element can be moved so far in the opening direction by pushing the actuation shaft that it is against the magnet unit. If the actuation shaft is pushed with great force this can lead to a deformation of the surface of the armature plate which can adversely affect the function of the stop valve. In particular it is possible for the deformed surface of the armature plate no longer to be able to be held in the open position by the magnet unit, because too great an air gap exists between the armature plate and the magnet unit as a result of the deformed surface.
Document WO 2012/080055 shows a gas valve unit for controlling a gas throughput guided to a gas burner of a gas appliance, wherein the gas valve unit has a valve housing and an actuation shaft for adjusting an opening cross section of the gas valve unit and an additional stop valve. A movement of the actuation shaft is able to be transmitted here to the stop valve by means of a linearly displaceable connection element. The connection element in this case has at least one spring. The spring can act here to prevent the shaft being pushed too far.
The necessary stiffness of the spring requires a certain wire diameter of the spring. The wire diameter and the volume of the spring required thereby reduce the throughflow area for the gas throughput to be guided. This results in a falling pressure of the gas throughput. Furthermore the stiffness of the spring must be large enough in order, in normal operation, only to cause a small or very small deformation of the spring. However the stiffness may also not be too high, in order to keep a maximum deformation force below a specific threshold. Overall relatively high design requirements are imposed on the spring.